This invention relates to an improvement for stab-type couplings or couplings in which assembly of a smooth wall tube to a coupling body is accomplished by pushing or thrusting the tube into the coupling body. Gripping of the tube surface and resistance to attempted withdrawal is based on the "Chinese finger" principle. Retaining or gripping means cooperates with the tube such that the greater the pull out force, the more securely the tube becomes seated within the coupling. The subject invention provides an improvement for the general type of coupling structure disclosed in the commonly assigned U.S. patent application Ser. No. 899,813, filed Apr. 25, 1978, now U.S. Pat. No. 4,229,025 issued Oct. 21, 1980. The teachings of this patent are incorporated hereinto by reference.
Stab type couplings have been known in the art for a considerable period of time. Generally, such couplings are relatively easy to install and merely require severing the end of a pipe or tube at a right angle and then chamfering the tube end to facilitate ease of insertion into a coupling body. One type of stab coupling which is often used is comprised of a pair of coupling bodies joined together in a fluid tight relationship so as to accommodate coupling of adjacent end portions of a pair of pipes or tubes. While such coupling constructions perform a valuable function, some undesirable characteristics are present in certain applications and/or installations. These undesirable characteristics can, however, also become apparent in other types of coupling configurations and applications.
More particularly, in joining adjacent end portions of a pair of pipes or tubes, it is often desired to affix one end of a double ended coupling assembly to one of the pipes and to then install the second pipe to the other end of the coupling assembly at a later point in time. This is often the case where, for example, a natural gas supply line is installed underground to extend from a gas main to at least the general site of a residential or commercial building under construction or contemplated for construction. In that situation, one end of the coupling assembly is installed at the terminal end portion of the underground supply line. A terminal end portion of a second pipe or line is then installed into the coupling other end at some later date and this second line typically extends to a gas meter or the like which has been placed or installed subsequent to installation of the original supply line. Quite often, the coupling is buried beneath ground level or otherwise exposed to the elements after installation onto the supply line. In that case, the end of the coupling assembly which has not yet been joined with the second or associated pipe can be damaged. Such damage, in turn, affects or compromises the integrity of the final coupled joint.
Due to the foregoing problems, it has been considered desirable to provide an improvement for stab type coupling arrangements which would protect the interior of the coupling bodies until such time that they are to be placed into use as by receiving associated pipes or tubes. This protection should be cost effective and allow easy removal when and as desired. The subject invention meets these needs in a simple and reliable manner.